Population Cycles

Question 1

How long do cycles commonly go for?

Answer 1

10 years (hare-lynx) or 3-4 year cycles (lemmings)

Question 2

What are 5 extrinsic mechanisms for cycles?

Answer 2

Periodic drivers
Random environmental disturbances
Climate
Lunar cycles -> longer breeding season and increased food every 9.3 years
Sun spots: variations in solar radiation intensity which alters plant growth and peaks every 11 years

Question 3

What are 3 intrinsic mechanisms for cycles?

Answer 3

Inter and intra specific interactions (trophic-level interactions) -> plant-herbivore, predator prey
Demographic stochasticity -> random births and deaths (quasi-cyclic)
Time lags -> delayed sensitivity to K, overshooting K

Question 4

What is the difference between a fluctuating population and a cycling population?

Answer 4

Cycling populations have a regular occurrence, while fluctuating populations are random peaks

Question 5

When do boom and bust “cycles” occur?

Answer 5

When population growth is closely tied to one limiting factor (tent caterpillars)